[9.0](backport #5715) re-enable CGO and buildmode pie

[mergify]

What is the problem this PR solves?

Re-enable CGO and buildmode pie to restore fleet-server metrics on darwin

How does this PR solve the problem?

How to test this PR locally

Design Checklist

• I have ensured my design is stateless and will work when multiple fleet-server instances are behind a load balancer.
• I have or intend to scale test my changes, ensuring it will work reliably with 100K+ agents connected.
• I have included fail safe mechanisms to limit the load on fleet-server: rate limiting, circuit breakers, caching, load shedding, etc.

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool

Related issues

---

This is an automatic backport of pull request #5715 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 693bd7b has failed:

On branch mergify/bp/9.0/pr-5715
Your branch is up to date with 'origin/9.0'.

You are currently cherry-picking commit 693bd7b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   magefile.go

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[prodsecmachine]

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[pchila]

Disabling CGO in 9.0 was embedded in #5429 (the CGO flag was handled in Makefile). However, that change has been overwritten by merging #5423 and overwriting any modification done in the Makefile.
There's no need to backport this change on 9.0.